Tasmanian devils hit by climate change before facial tumour devastation, study finds

admin | 杭州桑拿
4 Dec 2018

Low genetic diversity: A facial tumour disease has caused an about 80 per cent decline in the population of tasmanian devils. Photo: Devil ArkTasmanian devil populations had already plummeted before a facial tumour disease ravaged the species, due to dramatic shifts in the climate, Australian researchers have found.

While the iconic mammal is now confined to the Apple Isle, it was widespread across Australia more than 100,000 years ago.

More recently, the contagious facial tumour disease has caused an 80 per cent decline in contemporary devil populations since it was first reported in 1996.

Population geneticist Anna Bruniche-Olsen said the reason the facial tumour disease had been so devastating was because devil populations had low genetic diversity, meaning individuals had a limited capacity to survive the disease.

This low genetic diversity combined with the spread of disease and climate change are considered serious threats to the species’ long-term survival.

Ms Bruniche-Olsen, a PhD student at the University of Tasmania, set out to investigate what happened to the devil during its evolution to induce such low genetic diversity.

She hypothesised that four historical events could have been responsible: the spread of the facial tumour disease, bounty hunting of devils and Tasmanian tigers during early European settlement and two shifts in the climate – one a few thousand years ago and another more than 20,000 years ago.

Using the largest genetic data set compiled for devils, Ms Bruniche-Olsen built a series of ancestral trees that stretch far back in time.

“Depending on the shape of those trees, you can identify bottlenecks, stable population sizes or even population expansion,” she said.

Ms Bruniche-Olsen and her colleagues found a climate change event between 3000 and 5000 years ago caused a severe contraction in the devil’s population, which significantly reduced their genetic diversity.

Specifically, an increase in El Nino–Southern Oscillation (ENSO) activity, leading to a more arid climate, would have reduced food and shelter for devils, she said.

“We found an over 80 per cent [population] decline following this more arid period a couple of thousand years ago,” she said.

The study also found evidence that the last glacial maximum more than 20,000 years ago also had a measurable impact.

Ms Bruniche-Olsen said despite the effect of these events on devil populations the species had continued to survive low genetic diversity for thousands of years.

The group’s results have been published in the scientific journal Biology Letters.

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